1. Field of the Invention
The present invention relates to an optical disk apparatus for optically recording signals to an information carrier and reproducing the recorded signals by using light beams from light sources, such as lasers.
2. Related Art of the Invention
Optical disk apparatuses for playing back CD audio and CD-ROM usually use a laser light source with a wavelength of 780 nm.
However, a laser light source with a wavelength of 650 nm is used for high-density optical discs (disks having higher density and larger capacity than CD, and simply referred to as SD).
An apparatus has been proposed, which is provided with a laser with a longer wavelength of 780 nm for CD, and a laser with a shorter wavelength of 650 nm for high-density disks, whereby the laser with the longer wavelength of 780 nm is used to play back CD and CD-R, and the laser with the shorter wavelength of 650 nm is used to play back the high-density disk, SD.
In such an apparatus, it is unknown whether the disk having been loaded in the apparatus is CD or a density disk, SD. To make distinction, each of the two lasers is turned on, and focus servo control and tracking control are carried out, thereby to check whether the disk can be played back or not.
However, in the case that CD-R has been loaded, if laser light with the shorter wavelength is cast, and focus control and tracking servo control are carried out, the light beam from the laser is usually converged and cast to an area ranging from a quarter to a half of one round on the recording film of the disk, thereby causing a problem of erasing recorded information. The erasure of the information is serious to the extent that it cannot be recovered even when error correction is attempted, and the information may not be reproduced. The erasure occurs because of the following reason. Since the organic dye layer of the CD-R has usually been designed to have an optimal reflection characteristic at 780 nm, if laser light with a 650 nm or less is cast, the light is not reflected but absorbed. Therefore, it is difficult to detect the intensity of the reflected light corresponding to information marked on the recording film and to reproduce the information. In addition, the spot of the light beam becomes small and has high power per unit area, and the recording film itself has an absorption characteristic, whereby the recorded information may be erased.
Furthermore, in the case of the above-mentioned conventional optical disk apparatus, when the CD playback speed is increased to 6xc3x97, 12xc3x97 and 24xc3x97, the wobbling acceleration and the eccentricity acceleration of the disk increase in proportion to the square of the playback speed (rotation speed) of the disk. As a result, the wobbling acceleration and the eccentricity acceleration may exceed the ranges made allowable by the gains of the focus control and tracking control depending on variations in the disk and variations in the chucking of the disk, whereby control cannot be pulled in, and a problem of disabling start may be caused.
Moreover, it is difficult for the spindle motor to have a constant torque characteristic in the range of high-speed rotation, such as 24xc3x97, to low-speed rotation, such as the standard speed. In addition, the spindle motor itself has variations. With these taken into consideration, the rotation control of the disk becomes unstable, and this unstable control causes jitter in reproduced signals, thereby causing a problem of low performance.
The present invention is intended to solve the problems encountered in the above-mentioned conventional art, and proposes a control method at the start of operation for reproduction (or recording) on CD, CD-R and novel high-density disks. In addition, the present invention also proposes a method of stably pulling in focus control and tracking control, and a method of stably carrying out rotation control, and provides an apparatus for playback and recording on novel high-density optical disks, as well as playback on CD at high performance.
In the present invention, distinction is generally made to determine the type of disk before focus control and tracking control. The converged beam of light thus strikes the recording surface of the disk for a very short time (several milliseconds). Even if one of information marks is lost as a result, the lost mark can be corrected sufficiently, whereby no problem is caused in the reproduction of information.
Furthermore, in an apparatus provided with two or more lasers with longer and shorter wavelengths in accordance with the present invention, for example, in an apparatus provided with three lasers, the light of a laser 1 with the longest wavelength is first cast, and distinction is made to determine whether a loaded disk is CD, CD-R or not in a condition without focus control and tracking control. If the disk is not CD, CD-R, the light of the laser 2 with the second longest wavelength is cast next, and distinction is made to determine whether the loaded disk is a high-density disk or not in the condition without focus control and tracking control in a similar way. If the disk is not a high-density disk, the light of the laser 3 with the shortest wavelength is cast, and distinction is made to determine whether the loaded disk is a super high-density disk or not in the condition without focus control and tracking control in a similar way. The distinction proceeds in this order. When the light of each laser is cast and when the loaded disk is determined to be the type of disk to be played back by using the laser as the result of the distinction, focus control and tracking control are carried out for the first time, whereby binary operation and error correction are carried out, and information on the disk is reproduced.
Furthermore, in the present invention, an apparatus with high reproduction power (reproduction-compatible apparatus for disks, such as CD-RW) is configured to carry out emission at low power during the above-mentioned distinction. Therefore, even if laser light with a shorter wavelength should be cast to a disk, such as CD-R or the like, because of an error in the distinction, information can be prevented completely from being erased.
Next, configurations relating to the present application will be described below.
The first configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, an amplitude detection means for measuring the amplitude of said signal of said convergence condition detection means, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when one of said light sources with a predetermined wavelength is turned on, and when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of a signal from said amplitude detection means; if said light source with said predetermined wavelength is not compatible with the type of said loaded information carrier having been subjected to the distinction, another light source with a different wavelength is turned on, and said apparatus eventually finds a light source compatible with the type of said located information carrier and then drives said focus control means.
With the above-mentioned first configuration in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the laser passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, and the amplitude of a focus error signal (FE), which is delivered from the convergence condition detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is compared with a predetermined distinction value to make distinction to determine whether the optical disk is CD, CD-R or SD. If the loaded optical disk is CD, CD-R, focus control and tracking control are carried out immediately, information (TOC information and the like) on the optical disk is read, and a standby condition is reached. If the loaded optical disk is SD other than CD, the light source with a wavelength of 780 nm is turned off once, and another light source with a shorter wavelength (for example 650 nm) is turned on. The light beam generated from the light source passes through the converging leans used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier, focus control and tracking control are carried out, information (control track information and the like) on the optical disk is read, and a standby condition is reached.
The second configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding the convergence condition of said light beam on said information carrier, a total light amount detection means for outputting a signal corresponding to the amount of light reflected from said information carrier, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when one of said light sources with a predetermined wavelength is turned on, and when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of a signal from said total light amount detection means; if said light source with said predetermined wavelength is not compatible with the type of said loaded information carrier having been subjected to the distinction, another light source with a different wavelength is turned on, and said apparatus eventually finds a light source compatible with the type of said loaded information carrier and then drives said focus control means.
With the above-mentioned second confirmation in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the light source passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, and the amplitude of a total light amount signal (AS), which is delivered from the total light amount detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is compared with a predetermined distinction value to make distinction to determine whether the optical disk is CD, CD-R or SD. If the loaded optical disk is CD, CD-R, focus control and tracking control are carried out immediately, information (TOC information and the like) on the optical disk is read, and a standby condition is reached. If the loaded optical disk is SD other than CD, the light source with a wavelength of 780 NM is turned off once, and another light source with a shorter wavelength (for example 650 nm) is turned on. The light beam generated from the light source passes through the converging lens used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier, focus control and tracking control are carried out, information (control track information and the like) on the optical disk is read, and a standby condition is reached.
The third configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carrier or for recording information to plural types of information carriers, comprising two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, a reproduction signal detection means for detecting the amplitude of an information signal recorded on said information carrier or the amplitude of a signal obtained by the envelope detection of said information signal, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when one of said light sources with a predetermined wavelength is turned on, and when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of a signal from said reproduction signal detection means; if said light source with said predetermined wavelength is not compatible with the type of said loaded information carrier having been subjected to the distinction, another light source with a different wavelength is turned on, and said apparatus eventually finds a light source compatible with the type of said loaded information carrier and then drives said focus control means.
With the above-mentioned third configuration in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the light source passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, and the amplitude of an RF envelope signal (RFENV), which is delivered from the reproduction signal detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is compared with a predetermined distinction value to make distinction to determine whether the optical disk is CD, CD-R or SD. If the loaded optical disk is CD, CD-R, focus control and tracking control are carried out immediately, information (TOC information and the like) on the optical disk is read, and a standby condition is reached. If the loaded optical disk is SD other than CD, the light source with a wavelength of 780 nm is turned off once, and another light source with a shorter wavelength (for example 650 nm) is turned on. The light beam generated from the light source passes through the converging lens used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier, focus control and tracking control are carried out, information (control track information and the like) on the optical disk is read, and a standby condition is reached.
The fourth configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising a rotation means for rotating said information carrier, two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, and a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, wherein at the start or restart of said apparatus and with said rotation means remained nonoperable, when each of said light sources is turned on and light with a wavelength corresponding to said light source is cast, and when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, said apparatus makes distinction between the presence or absence of said information carrier on the basis of a signal obtained from a predetermined means is: (1) a signal from said convergence condition detection means, (2) a total light amount signal corresponding to the amount of light reflected from said information carrier, (3) an information signal recorded on said information carrier or a signal obtained by the envelope detection of said information signal, or a signal obtained by combining a plurality of signals of these signals.
With the above-mentioned fourth configuration in accordance with the optical disk apparatus of the present invention, while a spindle motor used as the optical disk rotation means is stopped, a laser with a longer wavelength of 780 nm is turned on first, a converging lens used as the converging means is moved up and down (close to and away from) with respect to a disk by driving a focus actuator used as the first movement means, the amplitudes of a focus error signal, a total light amount signal, signal RF and the like generated during the movement are detected. On the basis of the detected values, the apparatus makes distinction to determine whether a disk has been loaded or not. Next, a laser with a shorter wavelength of 650 nm is turned on, the converging lens used as the converging means is moved up and down (close to and away from) with respect to a disk by driving the focus actuator used as the first movement means, and the amplitudes of the focus error signal, the total light amount signal, the signal RF and the like generated during the movement are detected. On the basis of the detected values, the apparatus makes distinction to determined whether a disk has been loaded or not. As described above, the distinction is made by using the lasers with different wavelengths. Therefore, if a disk has been loaded, the detected amplitudes become significant when either of the lasers is active, whereby the accuracy of detection and distinction can be improved. Furthermore, since the spindle motor is stopped, even if the laser light with the shorter wavelength is cast to a dye-based disk, such as CD-R, the spot of the light can be limited to an error correctable size of a few microns or less, whereby a problem of recorded data damage can be prevented. In addition, since the turntable for accommodating a disk and the clamp for holding the disk are not rotated during the distinction, it is possible to prevent noised and damage which may be caused if the turntable and the clamp are rotated while no disk is loaded.
The fifth configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, an amplitude detection means for measuring the amplitude of said signal of said convergence condition detection means, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, and when each of said light sources is turned on and light with a wavelength corresponding to said light source is cast, a signal obtained from said amplitude detection means in this emission condition is stored in a storage means, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of the data stored in said storage means, and said apparatus finds a light source compatible with the type of said loaded information carrier and the drives said focus control means.
With the above-mentioned fifth configuration in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the light sources passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, the amplitude of a focus error signal (FE), which is delivered from the convergence condition detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in a DSP, RAM in a microcomputer or the like used as the storage means. Next, the light source with a wavelength of 780 nm is turned off once, and another light source with a shorter wavelength (for example 60 nm) is turned on. The light beam generated from the light source passes through the converging lens used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier. The focus actuator is driven, and the amplitude of a focus error signal (FE), which is delivered form the convergence condition detection mean and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in the DSP, RAM in the microcomputer or the like used as the storage means. The stored amplitude values of the signals FE are compared with each other and subjected to arithmetic operation to make distinction to determine the type of the loaded disk. Depending on the result of the distinction, predetermined starting parameters are set. Focus control and tracking control are carried out, information (TOC information, control track information and the like) on the optical disk is read, and a standby condition is reached.
The sixth configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising two or more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, a total light amount detection means for outputting a signal corresponding to the amount of light reflected from said information carrier, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when said movement means is driven to move said converging means close to and then away from said information carrier or away from and then close to said information carrier, and when each of said light sources is turned on and light with a wavelength corresponding to said light source is cast, a signal obtained from said total light amount detection means in this emission condition is stored in a storage means, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of the data stored in said storage means, and said apparatus finds a light source compatible with the type of said loaded information carrier and then drives said focus control means.
With the above-mentioned sixth configuration in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the light source passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, and the amplitude of a total light amount signal (AS), which is delivered from the total light amount detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in a DSP, RAM in a microcomputer or the like used as the storage means. Next, the light source with a wavelength of 70 nm is turned off once, and another light source with a shorter wavelength (for example 650 nm) is turned on. The light beam generated from the light source passes through the converging lens used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier. The focus actuator is driven, and the amplitude of a total light amount signal (AS), which is delivered from the total light amount detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in the DSP, RAM in the microcomputer or the like used as the storage means. The stored amplitude values of the signals AS are compared with each other and subjected to arithmetic operation to make distinction to determine the type of the loaded disk. Depending on the result of the distinction, predetermined starting parameters are set. Focus control and tracking control are carried out, information (TOC information, control track information and the like) on the optical disk is red, and a standby condition is reached.
The seventh configuration of the present invention is an optical disk apparatus for reproducing information from plural types of information carriers or for recording information to plural types of information carriers, comprising two more light sources with different wavelengths, a converging means for converging a light beam emitted from each of said light sources on said information carrier, a movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a convergence condition detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, a reproduction signal detection means for detecting the amplitude of an information signal recorded on said information carrier or the amplitude of a signal obtained by the envelope detection of said information signal, and a focus control means for driving said movement means in accordance with said output signal of said convergence condition detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, wherein at the start or restart of said apparatus, before said focus control means is driven, when said movement means is driven to move said converging means close to and then away form said information carrier or away from and then close to said information carrier, and when each of said light sources is turned on and light with a wavelength corresponding to said light source is cast, a signal obtained from said reproduction signal detection means in this emission condition is stored in a storage means, said apparatus makes distinction to determine the type of said loaded information carrier on the basis of the data stored in said storage means, and said apparatus finds a light source compatible with the type of said loaded information carrier and then drives said focus control means.
With the above-mentioned seventh configuration in accordance with the optical disk apparatus of the present invention, a laser with a wavelength of 780 nm used as the light source with a longer wavelength for CD, CD-R is turned on, and the light beam generated from the light source passes through a converging lens used as the converging means, and is converged and cast to a loaded optical disk used as the information carrier. In addition, a focus actuator used as the movement means is driven, and the amplitude of an RF envelope signal (RFENC), which is delivered from the reproduction signal detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in a DSP, RAM in a microcomputer or the like used as the storage means. Next, the light source with a wavelength of 780 nm is turned off once, and another light source with a shorter wavelength is turned off once, and another light source with a shorter wavelength is turned on. The light beam generated from the light source passes through the converging lens used as the converging means, and is converged and cast to the loaded optical disk used as the information carrier. The focus actuator is driven, and the amplitude of an RF envelope signal (RFENV), which is delivered from the reproduction signal detection means and obtained when the light beam is moved close to and away from the optical disk, is measured. The measured value is stored in the DSP, RAM in the microcomputer or the like used as the storage means. The stored amplitude values of the signals RFENV are compared with each other and subjected to arithmetic operation to make distinction to determine the type of the loaded disk. Depending on the result of the distinction, predetermined starting parameters are set. Focus control and tracking control are carried out, information (TOC information, control track information and the like) on the optical disk is read, and a standby condition is reached.
The eighth configuration of the present invention is an optical disk apparatus comprising a rotation means for rotating an information carrier at a predetermined rotation speed, a converging means for converging a light beam on said information carrier, a first movement means for moving the converged spot of the said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a focus error detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, a focus control means for driving said first movement means in accordance with said output signal of said focus error detection means and for performing control so on said information carrier becomes substantially constant, a second movement means for moving said converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the track on said information carrier, a track error detection means for outputting a signal corresponding to the relationship between said light beam and said track, and a tracking control means for driving said second movement means in accordance with said output signal of said track error detection means and for performing control so that said converged spot of said light beam on said information carrier properly scans along said track, wherein said focus control means or said tracking control means is activated at the start of said apparatus immediately after said rotation means is driven and before said information carrier reaches a predetermined rotation speed.
With the above-mentioned eighth configuration in accordance with the eighth optical disk apparatus of the present invention, before the rotation speed of an optical disk used as the information carrier reaches a predetermined value, that is, before eccentricity acceleration and wobbling acceleration become large, focus control and tracking control are carried out, and information (TOC, control track information and the like) on the optical disk is read. After the rotation speed reaches the predetermined value, a standby condition is reached.
The ninth configuration of the present invention is an optical disk apparatus comprising a rotation means for rotating an information carrier at a predetermined rotation speed, a converging means for converging a light beam on said information carrier, a first movement means for moving the converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the surface of said information carrier, a focus error detection means for outputting a signal corresponding to the convergence condition of said light beam on said information carrier, a focus control means for driving said first movement means in accordance with said output signal of said focus error detection means and for performing control so that the convergence condition of said light beam on said information carrier becomes substantially constant, a second movement means for moving said converged spot of said light beam converged by said converging means in a direction substantially perpendicular to the track on said information carrier, a track error detection means for outputting a signal corresponding to the relationship between said light beam and said track, and a tracking control means for driving said second movement means in accordance with said output signal of said track error detection means for performing control so that said converged spot of said light beam on said information carrier properly scans along said track, wherein if said focus control means or said tracking control means is unable to operate at the start of said apparatus after said information carrier has reached a predetermined rotation speed by using said rotation means, the rotation speed of said rotation means is reduced, and said focus control means or said tracking control means is activated again.
With the above-mentioned ninth configuration in accordance with the ninth optical disk apparatus of the present invention, an optical disk used as the information carrier is rotated at a predetermined rotation speed. At the rotation speed, focus control and tracking control are pulled in. If the pull-in ends in failure, and the focus control and tracking control are not activated, the rotation speed of the disk is lowered, and focus control and tracking control are pulled in again. If the focus control and tracking control are activated at the rotation speed, information (TOC, control track information and the like) on the optical disk is read, and a standby condition is reached.
The tenth configuration of the present invention is an optical disk apparatus comprising a rotation means for rotating an information carrier, a rotation control means for performing control so that said rotation means is rotated at a predetermined rotation speed, a gain switching means for switching the gain of said rotation control means, a rotation speed measurement means for measuring the rotation speed of said rotation means, and a rotation speed switching time measurement means for measuring the time required until a predetermined first rotation speed is raised to a predetermined second rotation speed on the basis of the measured value of said rotation speed measurement means, wherein said gain is switched by said gain switching means on the basis of the measured value of said rotation speed switching time measurement means.
With the above-mentioned tenth configuration in accordance with the optical disk apparatus of the present invention, when an optical disk used as the information carrier is rotated at a predetermined rotation speed, the time required until a first rotation speed is raised to a second rotation speed is measured. The control gain for a spindle motor used as the rotation means is switched depending on the measured time.
The eleventh configuration of the present invention is an optical disk apparatus comprising rotation means for rotating a information carrier, rotation control means for making a rotation speed of said rotation means at a predetermined value, gain switching means for changing a gain of said rotation control means, rotation speed measurement means for measuring the rotation speed of said rotation means, rotation changing period measurement means for measuring such a period that said measured rotation speed becomes a second predetermined speed form a first predetermined speed on the basis of the output of said apparatus judges the presence or absence of said information carrier on the basis of said time required until the rotation speed of said rotation changing period measurement means.
With the above-mentioned eleventh configuration in accordance with the optical disk apparatus of the present invention, when an optical disk used as the information carrier is rotated t a predetermined rotation speed, the time required until a first rotation speed is raised to a second rotation speed is measured. Whether a disk has been loaded or not is determined depending on the measured value. Therefore, the presence or absence of a disk can be determined in a period between the time when the motor is rotated and the time when the rotation speed of the motor reaches the predetermined value, whereby the time for starting can be shortened.